When pharmacological agents are unable to improve RV function, surgeons must rely on mechanical means to restore blood flow to the pulmonary circulation and left ventricle. Current options for mechanical assist include: centrifugal pumps; positive displacement pumps; and right-sided balloon counterpulsation. The drawback common to all these mechanisms is that they require invasive, time-consuming procedures to secure requisite cannulae and/or anastomoses to the pulmonary artery (unlike IABP assist of the left ventricle which can be positioned and retracted through a femoral artery cutdown).
The present invention was developed to provide a quick and simple means to assist the failing right ventricle. The inspiration for the present invention was the technique of cardiopulmonary resuscitation, in which the chest wall is physically compressed to cause ejection of blood from an arrested heart. The idea was to use expansion/deflation of a balloon within the chest cavity to achieve a similar result. It was believed intuitively that this approach would be more successful for RV assistance because the pulmonary circulation is a low resistance circuit that operates at a pressure 25% of that for the systemic circulation.
The present invention, unlike those currently available, allows minimally-invasive RV assist through a small subxiphoid incision. The expanding and collapsing mechanism can be rapidly deployed and is positioned in the anterior mediastinum. Expanding and collapsing mechanism removal can be effected by simply retracting the balloon from the pericardial space in a manner similar to removing a chest tube.
A discussion of RV assist devices and the treatment of RV failure appears in a review article by R. Higgins and J. Elefteriades titled "Right Ventricular Assist Devices and the Surgical Treatment of Right Ventricular Failure", Cardiology Clinics, Volume 10, Number 1, Feb. 1992, incorporated by reference herein.
Some characteristics which separate the present invention from other compression devices or RV assist devices currently on the market are its:
low cost PA1 mechanical simplicity PA1 ease of use (esp. insertion and removal) PA1 does not encircle the heart or directly compress the LV PA1 and designed to assist the RV with LV assistance as a secondary consideration.